/Engine/Source/Editor/PropertyEditor/Public/IDetailPropertyExtensionHandler.h
Gives the extension handler a chance to add extension widgets to the widget row. Typically, an extension handler can do so by using InWidgetRow.ExtensionContent(), but it can also modify other aspects of the widget row as well.
virtual void ExtendWidgetRow ( [FDetailWidgetRow](API\Editor\PropertyEditor\FDetailWidgetRow) & InWidgetRow, const [IDetailLayoutBuilder](API\Editor\PropertyEditor\IDetailLayoutBuilder) & InDetailBuilder, const [UClass](API\Runtime\CoreUObject\UObject\UClass) * InObjectClass, [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [IPropertyHandle](API\Editor\PropertyEditor\IPropertyHandle) > PropertyHandle )